1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head, and more particularly, to a method of manufacturing a piezoelectric type liquid ejection head.
2. Description of the Related Art
There are image forming apparatuses, such as inkjet printers, which employ a piezoelectric type print head (liquid ejection head) that uses the displacement of piezoelectric elements. As a structure for a piezoelectric element, for example, a common electrode is formed on the whole surface of a diaphragm which constitutes the upper surface of a plurality of pressure chambers, and piezoelectric bodies and individual electrodes are formed to overlap each other on the common electrode at positions corresponding to the pressure chambers. When a voltage is applied to a piezoelectric element, the piezoelectric body is displaced due to a lateral piezoelectric effect, and the volume of the pressure chamber changes through the diaphragm, the ink accommodated in the pressure chamber is pressurized, and an ink droplet is ejected from the nozzle connected to the pressure chamber.
In a piezoelectric type print head of this kind, in order to improve the energy conversion efficiency when converting the electrical energy applied to the piezoelectric elements into the kinetic energy of the ink droplets when ink is ejected, it is important that the diaphragm is thin, having approximately the same thickness as the piezoelectric bodies. However, if the diaphragm is formed to a thin dimension, then the strength of the diaphragm declines so that it becomes difficult to form the piezoelectric bodies directly onto the diaphragm.
Therefore, methods have been proposed in which piezoelectric bodies, and the like, are formed on a transfer substrate which is different to the diaphragm, whereupon the piezoelectric bodies, and the like, formed on the transfer substrate are transferred to the diaphragm (see, for example, Japanese Patent Application Publication Nos. 2003-309303, 2002-237626, and 7-17196).
Japanese Patent Application Publication No. 2003-309303 discloses a method in which a porous layer and electrodes (individual electrodes) are formed on a transfer substrate (intermediate transfer body), a patterned piezoelectric film is formed thereon, then the piezoelectric film and a diaphragm are bonded together through a bonding layer made of metal or the like (common electrode), and the porous layer is broken so that the transfer substrate is peeled away from the electrodes and the piezoelectric film.
Japanese Patent Application Publication No. 2002-237626 discloses a method in which a noble metal film, a lift-off layer, a first electrode film, a transfer film having piezoelectric properties, and a second electrode are formed, in sequence, on a transfer substrate (first substrate), whereupon a diaphragm is bonded onto the second electrode, the lift-off layer is etched using an etchant so that the transfer substrate is peeled away, and the transfer film is transferred onto the diaphragm.
Japanese Patent Application Publication No. 7-171966 discloses a method in which a piezoelectric material is screen-printed onto a transfer substrate, the material is heated and calcined to form piezoelectric bodies on the transfer substrate, a common electrode is formed on a head substrate, piezoelectric material is printed or applied thinly onto the common electrode, the piezoelectric bodies are made to adhere closely to the piezoelectric material on the common electrode so as to correspond to the positions of pressure chambers, and then calcined, whereupon the transfer substrate is peeled away. Furthermore, Japanese Patent Application Publication No. 7-171966 discloses, as separate modes, a method which uses a piezoelectric material mixed with metallic powder instead of the common electrode formed on the head substrate, a method which uses an epoxy resin or low-melting-point glass instead of the piezoelectric material formed on the common electrode, or a method which interposes individual electrodes between the transfer substrate and the piezoelectric bodies when forming the piezoelectric bodies onto the transfer substrate.
In a process of patterning piezoelectric bodies onto a flat transfer substrate so as to correspond to the shape of the pressure chambers, as in the methods disclosed in Japanese Patent Application Publication Nos. 2003-309303, 2002-237626 and 7-171966, a method is used which forms a solid film and then divides the film into individual films by etching, sandblasting, or the like, or a method based on screen printing is used. However, in the former method, it is necessary to repeat the step of division each time a print head is manufactured, and hence there is a risk that variation may occur in the shape of the piezoelectric bodies, and furthermore, an increase in manufacturing costs results. Moreover, in the latter method, there is a risk that variation may occur in the thickness of the piezoelectric bodies.
Furthermore, if an epoxy resin or low-melting-point glass is used to bond together the piezoelectric material and the common electrode, as described in Japanese Patent Application Publication No. 7-171966, then there is no bonding stability, the electric field applied to the piezoelectric bodies declines because an insulating material is inserted between the piezoelectric bodies and the common electrode, and the displacement of the piezoelectric bodies falls.